Radio wise connecting cikciti e s



Oct. 30, 19230 R. BOWN ET AL RADIO WIRE CONNECTING CIRCUITS Filed April 26, 1921 4. Sheets-Sheet 1 Oct. 30 1923.

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RADIO WIRE CONNECTING CIRCUITS File-d April 26, 1921 4 Sheets-Sheet 3 wvamtow WWUBII ulumwul Oct. 30, 1923. M4723 R. BUWN ET AL RADIO WIRE CONNECTING CIRCUITS Filed April 26 192] 4 Sheets-Sheet 4 ggx Patented Oct. 30, 19230 UNITED STTES LMLZW arr'r RALPH BOWLT AND EDW'ARD L. NELSON, 01? EAST GRANGE, NEW JERSEY, lhSSIG-NOES TO AMZERICAN TELEPHONE AND TELEGRAPH COMPi-LNY, .A CORPORATION OF NEW RADIO WIRE CONNECTING CIRCUITS.

Application filed April 26, 1321.

To all whom it may concern:

Be it known that we, RALPH BowN and ltnwiino L. Nansen, residing at East Orange, in the county of Essex and State of New Jersey, respectively, have invented certain linprovenients in lftadio Wire Connecting Circuits, of which the following is a specification.

This invention relates to connecting circuits and more particularly to connecting or link circuits for establishing connections between wire lines and radio systems.

ltadio systems, as now developed, and particiilarly rad'io telepl'ione systems, involve a transniittin station and a receiving station, usually located some distance apart, as for example, a mile or so. In order to reduce reaction of the radio transmitter upon the radio receiver, the transmitting station may be provided with a plurality of channels for trz insniitting to each of several distant receiving stations and the receiving station may likewise be provided with a corresponding nrmiber oi receiving channels for simultaneously receiving messages 'from said distant stations. In order that the communication facilities provided by such a radio system n'iay be extended over wire telephone or telegraph circuits, it is desirable that some arrangement be provided 'lor liner-connecting any long distance telephone circuits, for example, with any one o'li' a number 01'? corresponding transmitting); and receiving channels of the radio system.

ilhere are certain factors which make the operation of a radio telephone system distinctly ditlerent in some important aspects from similar operation of wire or carrier circuits. The radio receiving station and. the radio transmitting station, although located a short distance apart, must be ln'ought to a common point with the toll line terminal so lhali they may be properly connected for a through circuit from wire to radio. it is turther desirable that this condition be duplicated at both the trans initting and receiving station of the radio system that is to say, duplicate arrangements should be installed at the two sta tions, which will allow the operation from either station oi any or all circuits iudependently.

Serial No. 464,668.

Each radio operator must be able to per form a nunilber of different operations. F or example, he must be able either to listen or to talk and listen simultaneously or independently on any and all radio channels. He must be able to monitor a call which has been set up between radio and wire without interrupting; also, he must be able to talk or listen either way on such a call. l urthernlore, the operator should be able before making the finalthrough connections on a call, to adjust the on either the transmitting or receiving side of the circuit so that a proper coinn'uniication will result. Arrangements are, of course, also necessary for signaling over the toll wire circuit o for signaling the distant radio stations. lt should be possible for any call to be monitored from the non-operating station; that is to say, it operation is being carried on from the receiving station board, it should, at the same time, be possible to monitor all connections from the transmittingstation board as well. Finally, provision must be made for the operator to cut over quickly and readily to an order wire connecting the transmitting and receiving station of the radio unit.

In accordance with the present invention, connecting or link circuits are provided and. so organized as to interconnect wire lines with radio channels, in such a manner as to satisfy the foregoing requirements. As it is obviously necessary that the two-wire toll line which is brought up to the radio station, must be split into a f u1r-wire circuit before connection with the radio transmitting," and receiving channels, there are two possible places in the circuit where the necessary switehing and operating arrangements may be introduced. These are in the two-wire line or in the "four-wire part oil the circuit. In accordance with the present invention, arrangements are provided for performing the switching operations in accordance with either of these methods.

The invention may now be more carefully understood from the following description, when read in connection with the accompanying drawing, 1 and E2, of which, illustrate switching circuits at the radio transmitter and radio receiver respectively of a radio system, E01? inter-connecting the system with wire lines, the switching arrangement being associated with the four- Wire part of the circuit; and Figs. 3 and et illustrate a similar arrangement in which the switching devices are provided in the twoavire part of the circuit.

Referring to Figs. 1 and 2, Fig. l illustrates the apparatus associated with the radio transmitter located at station A, and Fig. 2 illustrates the apparatus at a corresponding receiving station B located a short distance away, the two stations cooperating to simultaneously transmit to and receive from distant radio stations. L designates a toll line terminating at the station A, at which point it is branched through the usual hybridcoil into a circuit LE leadin to the radio transmitter and a circuit IETV leading from the radio receiver, the circuits LE and LW terminating in jacks JE and JW respectively. The line L is balanced in a well known n'ianner by.

means of networks N Associated with jack J E, is a drop SE or other form of signal responsive device, to indicate the transmission of ringing current over the toll line L,.' The cord circuit comprising conductors (ll/V, and CE is provided at station A for controlling the establishment of connections between the circuits LVV and LE and the radio transmitter T and receiver R. For this purpose the conductors CW terminates in the plugs PW and PW while conductors CE terminates in plugs PE, and PE,. When it is desired to establish connections to the radio transmitter and receiver directly at station A, the plugs PWV and PE may be inserted into jacks JW, and JE, which are. connected to circuits LVV and LE, respectively, the latter being connected by means of. conductors LE to the local transmitter T and the former extending over a circuit leading to the receiver R at the receiving station E. The radio transmitter T is merely conventionally indicated and comprises a transmitting antenna TA having associated therewith channels I, II and III for multiplex transmission. Only the apparatus associated with the channel I is indicated and this apparatus comprises a modulator M of any well known character as, For e3:- aniple, a vacuum tube modulator-said modulator being supplied with carrier current of radio frequency from a source 10. The telephone or other signaling currents are applied; to the modulator of the channel I over the circuit LE When the establishment of connections between the wire line and the radio system is to be controlled from the receiving station '13, the cord circuit illustrated in Fig. lniay be connected to jacks JVV and JE- which are connected to trunks TW -and TE leading from station A to station E. In this instance the cord functions merely as a patching cord to extend the circuits LIV and LE to station I3. The drop SlV may be associated with the jack JW to indicate to the operator at station A that a distant radio station desires to be connected to the wire line.

The cord circuit is provided with three switching keys, K K and K, all controlling the monitoring, listening and talking operations, and with ringing keys K, and K the former being arranged to transmit ringing current to the wire line and. the lat ter to transmit a ringing signal to the radio transmitter, in order to call a distant radio station. For the latter purpose the key N is arranged to alternately apply ringing current of two frequencies to the plug' lF These frequencies are preferably within the voice range, as for example, 700 cycles and 900 cycles, and the ringing apparatus of the radio station is so arranged, as will he later described, that it will respond when both ol these frequencies are applied alternately. but will not respond to either 'fl'( ,(]ll(ll( alone.

The keys K K and, K each have three positions in which they may be locked n any well known manner. The springs of the key K are so arranged that with ll 1. key lever in its normal position, the springs on either side of the key lever will he closed. hen the insulated element of the hey lever is shifted to the left, the springs on the in fthand side will remain closed, but those on the right-hand side will be open, so that the listening and monitoring apparatus will be disconnected from the radio side oi the system and will be connected to the wire side of the system eX ':lusively. hen the key lever is shifted in the opposite position. the right hand springs will remain closed and the lel't hand springs will. be permitted to open, so that the opcratofs apparatus will be connected to the radio side of the sy in one clusively. The keys K and K. are simila in construction to key K, except that in the neutral position of the key lever all of the springs are open and when the insulating element is shifted to the right. for example. all of the springs to the right will be closed. and when shifted to the left only the spri to the left will be closed. The key K tune tions to connect the operators talking and listening set either to a plug P0,, which may be connected to an order wire (I, through a jack J0 or to the cord circuit through key K When the key K is adjusted to connect the operators set with the cord set, the key K will determine whether the operators receiver will be connected to the circuit alone for monitoring purposes or whether both transmitter and re eirer will be connected to the circuit for talking and listening.

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The cord circuit shown at station identical in arrangement with that shown in station A, and need not be further described. This cord circuit enables the operator station 13 to control the establishi'ncnt of connections. between the wire line and the radio system. When the connections are 't o be controlled from station A the cord circuit may be used to enable the operator at station l3- to monitor a connection established at station. it, by inserting the plugs l ll and P in the jacks J l and illfi The drop ti l V may be associated with jack till for responding to ringingsignals incoming troni the radio system and the operator .3 set at station l3 may be connectedv to the order wire U through plug TQ and j aclr J U when the hey K is operated to shift the insulating element to the right.

The radio receiving apparatus comprises an antenna lid, with which may be associated a plurality oi receiving channels it, ll, and Till. The channels include suitable filtering apparatus li and i The receiving apparatus associated with the channell alone is illustrated. This apparatus includes a demodulator or detector ll which may be for example, of the balanced vacuum tube type, said do modulator being connected to the circuits lil l and LW leading; to the switchl'ioards at stations A. and B respectively. ll iiesiri l an amplifier AW may be provi ad in the output circuit of the demodulator D The ringing responsive apparatus associated with. the radio receiver comprises two tuned circuits l1 and 12 connected to the ou'tpi'it side olthe demodulaton these tuned circuits being" selective oi the detected nging 'li'equencii-is of". for example, 700 and 900 cycles. respectively. Vaoi'ium tube detectors if; and 14.- are associated with the two tuned circuits and these detectors control the ndividual windings of a polar relay Pi l. When the two frequencies oi, tor ei-iai'nple, int) cycles and 900 cycles are alternately eceived at sorne low frequency rate oi interruption as, for erarnple l6 interruptions per second. the winding oil relay l R will be alternately energized to shift the armature to the right and left at a corresponding low frequency rate thereby shitti the battery connections of a local circuit '1 :1 so that a low frequency alternatino, ring;- iw: iturrent of 16 cycles per second will be transmitted to the circuits LW and Til l7 to operate the drops t i l and. Tilat ions plugs i /V and lll into jacks vil i and il a. and by inserting the plugs Pll and i LJZ in jacks dil and vlil l The keys and it; will be in their normal positions and the gain controllingdevices (ll V and llll will be open so that the cord functions as a simple patching cord. lit a distant radio station signal is to be connected over line L1 a carrier frequency will be received by the antenna llili i. from the distant station, said carrier treip'ioncy being alternately modulated at a rate or in cycles per second, for example, in accordance with ringing frequencies of said 700 and 900 cycles. The detector D iunctions to detect from the carrier frequency the iicipiencies oi 700 to 960 cycles respectively, and these :lre uencies are selected by the circuitsl1 and 12 to cause the armature of the relay PR to vibrate at a rate of 16 cycles per second, thereby iin iiressinpg a ringing signal upon the coni'luetors Till and lil il to actuate the drops hll i and till he: the operator tation B is to handle the call, the opor at station A will ignore the drop and the operator at station B will answer the call by inserting the plugs lPl l and PE in the jacks 'l W and il l l The operator will throw the hey lil to open the letthand springs thereof and the i will. be shifted to close the rig htliiand lljt' desired, the operator may also sh'i it the key K to open its lei thand s 'n'inns. The operators transmitter and receiver will now be connected to the radio side of the system, the transmitter beingconnected to the circuit i an d the receiverbeing;connected to the circuit TIW The operatorwill therctore receive the detected voice message transmitted from the distant radio station, conununicatin r with the calling); station by means oi her transmitter which is connected to the circuit l il h. The operator is enabled to speak to the distant calling station by transmitting the voice current over the circuit lil l. and over the circuit Til to the .TilOtllllill'OI M that the carrier frequency supplied by the modulator M will be radiated by the antenna Tilt as modulated by the voice currents incoming from the circuit T1 The operator. having determined that the call is For the line ll may first adjust the gain due to theainplifie Al in bY HIP/ZUJQE oi the gain adjustin device til l this gain.

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adjusting device being connected between the ampliier AW, and the OPGI'ttiJOfiS receiver. The operator may also adjust the gain of the amplifier Aid, in the circuit leading to the radio transmitter, by adjusting the gain controlling device 5E at the same time throwing the switch 20 t its lower position in order to shift the connection of the operatorsreceiver from the key K, to the transmitting circuit LE t will be seen that the operators receiver is new connected to the output side of the amplifier R E and the gain controlling device will adjust the input current, the operator being enabled to deteri'nine when the adjustment is right by listening on the output side of the amplifier. The operator will then restore the switch 20 and shift the key K, to open the righthand springs, thereby disconnecting her set from the radio side of the system and connecting it to the wire side. The plugs PlN, and PE, will then be inserted in the jacks J W and 3E and the'ringing key K, will be actuated to transmit ringing current ver the circuit TVV through the cord conductor CWV, and over the circuit Ll V, to the toll line L Having signaled'the distant toll operator, the radio operator is enabled to communicute with the toll operator to pass information to the desired. connection. In conversing with the toll operator the radio operators transmitter will be connected to the circuit TE and the receiver to the circuit Til so that the transmission over these circuits will take place in directions opposite to the normal direction of transmission when the complete connection between the radio system and the wire system is set up.

The distant toll operator, havingobtained the desired subscriber, the key K, will be restored to its neutral position and the concuctors of the cord circuit will be extended through from the Wire part of the system to the radio part of the system. The called subscriber can now communicate with the calling radio station over a circuit as ifollows:

From the line l5 over the circuit LE conductors 0B,, trunk TE conductors (1E conductors LE includin the repeater AR,

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conductors Ill-l to the modulator M, and thence by radiation of the antenna TA to the distant station.

Transmission in the opposite direction from the calling radio station to the called subscriber takes place as tollows:

The received radio oscillations are impressed upon the receiving antenna RA, passed through the filter F detected by detector D amplified by amplifier AlV, and thentransmitted over the circuit Liv, conductors CW trunk TW' conductors CW and circuit LVV to the line L During the conversation the operator may listen in on the transmission from radio to wire without disturbing the connection, ly t rowing the hey K, to close the left; hand sprin s thereoi, the key ii, being, oi course, in position to connect the operators set with the various cords. tinder these circumstances, the talking current: incoming From the circuit if. to the ronductmv pass into the circuit 21 over the cw, wili lei'thaud contacts ol the key K over the circuit 22 and inner leithund contacts oi the key K, to the receiver. The operator .M. iv 7 0 contacts oit hey is, over the circuit 2 1, outer lcfiihand contact of the hey K, to the op- J 1 v l I v craters transmitter. lhe voice currents assin iroin the trunk "lll, to the radio l rw 1 l.

innsmitter will low into the circuit 23 and will be heard by the operator through the transformer 2:; which :iiiords a side tone connection. between the operators trans initter and receiver.

The operation when a subscriber desires to be connected over the toll line to a distant radio station will be somewhat similar. in this case ringing current will be trans mitted from the toll line L, over the circuit Ll"), conductors CE, and trunk (TE thereby actuating the drops SF, and FE The operator at station in response to the actuation of the drop f ll).. will plug into jacks ill V and Jill, and shift the hey ii t connect her "art to the wire side of the cord, the key K being in talking and listening position. Having ascertained the connection desired, the operator will insert the plugs PlV, and Phi, into the jacks .l W.. and J E and then shift the key If, to the opposite position and actuate the ringing hey K This will result in alternatel applying to the circuit Lll, currents o't 700 cycles and 900 cycles, respectively. 'lhcsc currents will be transmitted through the amplificr All, and over the circuit LE to the modulator M The carrier frequency from the source 10 will be modulated accordingly and radiated to the distant station where it may actuate the ringing apparatus siniilar to that illustrated in connection with the radio receiver at station l3.

Vvhen the distant operator answers the Call, the radio operator at station B may communicate with such operator at the same time adjusting the receiving gain by means of the transmission adjusting device (V As soon as the distant radio O)6I.f1il0l is ready to receive the call, the key K, can. be

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restored to normal position, thereby connecting the radio circuit through to the wire circuit. The gain ol? the amplifier Al), in the transmitting circuit may be adjusted as previously described, by shifting the switch to connect the receiver to the circuit LE and by adjusting the transmission device G13 The monitoring operation during the connection will be as previously described.

During any of these connections, the operator at station A will be enabled to monitor in exactly the same way as at station B, by suitable manipulation of the cord clrcuit keys and the operators at the two stations may communicate with each other at any time by shifting their keys K and it, to. close their righthand springs, thereby eonnectinp; the operator s sets to the plugs PO, and 0, respectively. These plugs Wlll be inserted in the jacks J0, and J0, respecti vely, associated with opposite ends of order wire U so that conversation may now proceed over the order Wire.

in the operation previously described it has been assiiimed that the operatm' at the receiving station B will be in charge of the establislmlent of connections. it is equally possible, however, to estz h the connections at station A. In this case the trunks TlV Til-1,, the cord circuits Gi l, and CE, at station B and the circuits WW and lnlll need not be used. The operator at station A. establishes the connection byinserting the plugs PW, and PE, in the jacks JW, and M5,. The ringing signal from a distant radio station will operate the drops SW, and SW, as previously described. i l/here the operator at station is to establish the connection from radio to wire in response to a call from a distant radio station, the operator at station A will. insert the plugs in the jacks as described and by proper manipulation of the keys loi and K,, the operator will be able to communicate with the distant radio operator. The mes sage currents t"a:nsmitted by the operator at station A. will pass over the circuits LE, tln'ough an amplifier AB, and over the circuit l ilt to the radio transmitter. In transmittin from the distant station to the operators receiver, the detected voice currents in the output circuit of detector l), at station. B will. be amplified by amplifier Jil and transmitted over the circuit Li and over the conductors (PW, ot the cord circuit to the operators receiver. The operation oi ringing the toll operator will be similar to that described in connection with that of setting up a call at station B and need not be further described. As the cord circuit at station it. is identical with that at station B, the monitoring, talking and listening operations of the operator will be the same as those already discussed. The adjustment of the gain of the repeater AW,

can be determined by setting the transmis sion. controlling element Gi l, of the upper pair of conductors of the cord circuit and the gain oi the amplifier AE, may be adjusted by means of the element GE the operators receiver being switched by means or the switch 30 into connection with the circuit LE The manner inv which a call incoming from the toll line L, is switched to the radio apparatus, will be obvious without further description, the connection being established by inserting the lefthand plugs of the cord circuit at station A into the jacks connected with the toll line, and by insertin the plugs PlV and PE into the jacks JTV, and JE,,.

The method of operation just described prevents the operator at station B from taking any part in the establishment of a connection. however, monitor on a receiving circuit, that is, on transmission from the radio re ceiver to the toll line, by inserting plugs BTW, and PE, into the jacks JW and M5,. The keys K K and K, being thrown to the proper positions for monitoring, this will connect the operators receiver to the circuit LW thereby permitting the operator to listen in on the received transmission.

In order to enable the operator at station B to monitor, talk and listen in the same manner as the operator at station A, when the connection is established through the cord circuit at station A, a slightly different method of operation may be employed. In order to obtain this result, the cord circuit at station B may be used as a patching cord by inserting the plugs PW, and .lll, into the trunk jacks, and the plugs PW, and PE, into the jacks JW, and Ji l The key Ti should be in neutral posi tion when the cord is to be used for patching purposes. With the circuit thus con-- .ected the operator at station A in response to a radio call actuating the drop Sil or in response to a toll. call operating the drop SE will complete the connection by inserting the plugsPlV, and PE, in the jacks Jil and did, as before, and by inserting the plugs PW, and into the jacks (l /V and 5B,. Transmission will now take place, both ways, through the cord circuit at both positions, and either operator may monitor or may-E talk and listen. l i locn connec tions are to be established in this manner. the gain controlling device GW, and GE, at station B should be open so that the adjustment of the gain will be under the con trol of the operator at station A.

llt will. be noted that the cord circuits are so arranged that an operator may monitor on any number of connections simultaneously. This may be done by throwing the key K, which is common to all of the cords, to such a position as to close its letthand The operator at station B may,

springs, the keys K individual to each of e cords being likewise thrown to close their lefthand springs. When the operator desires to use her set for establishing connections, however, the keys K of all other cord circuits than the one used in the establishing connection, should be in neutral position in order toprevent the conversation jbetweenthe operator and the calling parties from being transmitted to establish connections. Monitoring on all connections simultaneously-should therefore be taken careof by the operator at station B when the operator at station A is establishing connections, or vice versa.

The arrangement illustrated in Figs. 1 and 2 involves arrangement in which the toll line is split into a four-wire circuit, at the point Where it is brought up to the first position of the radio system, and the toll circuit is therefore extended through the two positions at the transmitter and receiver re spectively as a four-wire circuit.

A modified arrangement isillustrated in Figs. 3 and 4, in which the toll circuit is carried through thetwo stations as a twowire circuit and at the second of the two stations is split into a tour-wire connection,'one pair leading to the radio transmitter and the other to the radio receiver.

Referring to Figs. 3 and 4:, L designates a toll jline terminating at the transmitting station A in jack J,. A cord circuit C, is provided at this station, terminating into plugs P, and P for'use in extending the toll line to station B. A. trunk T extends between stations A and B, terminating at the former in a jack J and at the latter in a jack J At station B a similar cord circuit C terminating in plugs P and P, is provided for extending the trunk connec tion to the point at which the two-wire circuit is split into a tour-wire circuit. A jack J 4 is provided at this point and the two-wire circuit terminates in the usual hybrid coil arrangement whereby the circuit may be split into two branches, one branch LE leading to the radio transmitter and the other branchLVV leading to the radio receiver. The balancing network N, is provided for balancing the two-wire circuit.

Here again the establishment of a con nection may be under the control of the operator either at station A or B. It: the connection-is to be established at station A, the cord circuit G at station B will be used as a patching cord; if the connection is to be established at station B the cord circuit at station A will be used as a patchingcord. Both cord circuits are identical and are provided With controlling keys similar to those of the cord circuits shown inF igs; 1 and 2. The keys K and K and their connections, are identical to the corresponding keys in Figs. 1 and 2. The keys K and K are also similar in construction to the corresponding keys in Figs. 1 and 2, and perform somewhat the similar functions, but the circuit connections are slightly different. The key K for example, when its lefthand springs are closed, establishes a monitoring circuit, but the monitoring circuit does not extend to the conductors of the cord but extends over an independent connection 40 to a trunk connection LlV, leading from the station A to the output side of the amplifier AWV of the radio receiver at station B. In the talking and listening position of the key K, on the other hand, the operators transmitting andv receiving circuits are extended as four-wire circuits from the. righthand. contacts of the key K, and are then merged by means of a hybrid coil arrangement into a two-wire circuit bridged across the talking conductors of the cord (1,. The connections of the key K, at station B are similar, the monitoring con nections being established over conductors 4-3 leading to circuit LVV, on tho out put side of the amplifier Al while in the. talking and listening position of the key be transmitter and receiver of the operator are connected through a four-wire circuit. to a hybrid coil merging into a connection in bridged across the talking conductors oi" cord 0,.

The key K is arranged so that when in neutral position to the two ends of the cord will be connected together with the talking and listening connection -12 bridged across the cord. The four inner contacts of the key are normally closed in the neutral position and the two outer contacts are normally open. in this position. Vb-en the key is thrown to shift its insulating element to tlnleft, the normally closed springs Ht the light are open and the talking and listening connection extends toward the toll line F-Ii'lflsively and is disconnected from the radio part oi the system. The extreme lcl'ilianil contact of the key also closed to short-- circuit the circuit LE, over the conductors 41 to prevent any singing in the radi system due to the unbalancing oi the hybrid coil when the line side of the balancing circuit is open. When the key is shii'ted to the opposite position, the lctthand normally closed contacts are open and the talking and listening connections are to the radio side of the system exclusively. The cxtrnnw righthand contact oi the key is also closed to complete a circuit through the relay 45 which functions to disconnect the normal balancing network N, and substitute an auxiliary network N, so that the hybrid coil to take care of the balance under lhc changed impedance conditions due to the fact that the impedance of the operators set is different from that of the toll line. The key K is similar to the key K its 1 ,a-rasee extreme letthand contact controlling short circuit owr the circuit LE leading to the radio ti'ansinitte and its extreme righthand contact controllii r the relay to change the net worlr so o balance the operators set.

it; and K are :hose used in ordinar cord circuits c.: that the heys lanil v frequencies as deser l The train controllin5; devices ar not associated with two-wire :ord circuits in. Fi

x 8 and 4, but are included in the tour-wire p; rt ot the circuit, for example, the gain controlling device GE, and are bridged across circuit LE, leading); to the 'adio transmitter at statioi s it and B IGSPBClZlVOly, and the gain controlling devices tillV. and til l are hrii'lged across a. bridge cirruit 46 lead 111g trom the conductors lil l associating the 'adio receiver With the two-wire part ot the circuit.

Further de ails of the apps 'atus may now he understood. from the description of the operation which as follows:

Assuming that the oinpletion oft connectious to the radio systeu'i is to he controlled. at station it. the cord circuit C. at station A will be plugged into the jacks J and J to serve as a patching cord for extending the toll line L over the trunk where it terminates in the jack J In response to a ringingsigrual the drops SE, and SE will he actuated and the operator at .aation B, observing the actuation of the drop SE will. insert the plus; l of the cord. (l into the jack J and throw the hey hi so that its insulating; element is moved to the left. This closes the short circuit connection 50 across the i-omluctors lil l and prevents the singrin q' of the system 'fl'Otl'l the radio transniitter to the radio receiver due to unhah ance while the cord circuit is held open. By throwing the lrey K to close its righthand springs and the key to close its letthaud s irings. the operatofis set is connected over conductors t-lto the toll :ircuit, to the exclusion of the radio part of the system and the operator is enabled to converse with the calling; operator or subscril'ieif';

Upon obtaining the desired iutorniation as to the call which it will he assumed is to he extended over the radio channel illustrated, the operator inserts the nh'in; P in the aclr J and throws the key K in the. opp site direction to connect her set to the radio part or: the system exclusively. The

operator may then actuate the key K to tansniit ringing current over the conduo tors LE to the adio transmitter. l /hen the distant radio station answers, the hey hi may he thrown to neutral position and the conversation may he carried on over the wire circuit and over the radio system. Better-e finally (ZOIHPlQtiD "he connection the one ator adjusts the gains oi the amplifiers Al and lt dl. In order to adjust the grain oi the anu'ilitier All 1 the hey may he thrown to close its letthand springs. there'hy connecting; the operators receiver over ci cuit to the output side of the amplifier and. The gain controlling device filth. which is hridged across the output circuit of the amplifier n'iay then he adjusted so that the desired grain is obtained as deterniined by the sound in the operators ceiveix The operator may th n throw the switch 20 to its lower position thus bridging the receiver across the circuit LE on the output side of the amplifier The gain of this amplifier may he adjusted by means oi" the adjusting device tilt During; the continuai'ice oi? the conne tion the operator may monitor o the circuit leading to the radio receiver hy inaintaining; the key K in the position in which the lefthand springs are closed. lit the is thrown to the opposite position. the open ator will be enabled to listen and ta l; any time by reason of the :Fact that the operators set is hridn'ed across the cord cirnit through conductors 44;. By throwing the key K to close its letthand springs the operators set .iay he connected to the order wire (l so that the operator; at stations A and B may communicate with each other.

it. call from radio to wire is handled. in a somewhat similar manner. it ringing; nal incoming from a distant radio station operates the an iniratus in a manoe' similar to that descrilied in connection with Fig. 2,. and. transmits z. rin ggin e' curren; to conductors Li l and liil l thereby actuating; the drops Filth, and Fl d The operate at station B then plugs into the jacl: d] and throws the key K to shift its insulating element to the rig-ht. This connects the onerators set to the radio side 0'? the system exclusively and closes the 0. one right hand contact to complete a circuit through the relay 4115., wl'iich substitutes the halancingr arrmiecinent M tor the halancing arrange" ment M the former halanciup; arrangement asig'ned. to ha ancn the impedance of the operations set. Hat" 1 ascertained the conne *tion desired, the plug}; P will he iii-- serl'ei'l in the jack J and the ringing hey lt operated. During this period the lrcy n'iay he shiil ted to its opposite position to permit the radio operator to converse with the toll ooerai'or. l i hen the conversation is llli ready to proceed, the key K, will be again set in neutral position.

\V hen it is desired to complete connections from station A the cord circuit C at tion B will be used as a patching cord, an: as the cord circuit at station A identical with that at station 13, the operation of com-- pleting connections is the same, the on difference being thatthe operator observes the actuation of drops SE, and Y instead of drops SE and SW The key K, when its extreme lefthand contact is closed, short circuits the connection LE over onductors L1 to prevent singing between the radio transmitter and receiver when the hybrid coilis unbalanced. \Vhen the key is thrown to its opposite position, the extreme righthand springs control the circuit oi? the -rclay 45 over conductor 51 in a manner sinii lar to that described in connection with key K The adjustment of the gain may be controlled by means of the devices Gi l, and GE, the former of which is bridged across the output circuit of the amplifier AW through the circuit L N and the latter of which is bridged across the circuit LE on the output side oi the amplifier The gain may be observed through the operators receiver by throwing the key i, to close its lefthand springs when the gain of amplifier UV, is to be adjusted and by throwing the switch 30 to its lower position when the ga in of the amplifier AE, is to be adjusted. It will, of course, be understood that when the adjustment is to be made at station A the gain adjusting devices sta tion B will be disconnected, and when the adjustment is to be made at station B, those at station A will be disconnected.

The circuit arrangements hereinbetore described are quite flexible and adapt thernselves to a number of different methods oi operations varying somewhat from those described, and as these different methods of operationwill depend somewhat on the con not be attempted here to describe all of the possibilities inherent in the apparatus as these features will be readily apparent to one skilled in the art.

It will also be obvious that the general principles herein disclosed may be embodied in many other organizations widely different from those illustrated, without departing "from the spirit of the invention as defined in the following claims.

What is claimed is:

1. In a signaling system a radio transmitter and radio receiver, connections extending from said radio transmitter and said radio receiver to a common point, a hybrid coil and a balancing means for associating said connections with a two-wire terminal, a plurality of wire communication channels and a link circuit independent of said hybrid coil for associating said radio transmitter and receiver with any one oi said wire com munication channels.

2. In a signaling system a station having a radio transmitter thereat, a station having a radio receiver thcrcat, connections on tending to said radio transmitter and said radio receiver, said connections having tci minals at each station, a plur lity oi wire commiuiication channels havi terminals at one of said stations and means contr llable from each station for connecting any one of said wire communication channels lo said radio transmitter and receiver.

3. In a signaling system astation having a radio transmitter including a pluralily of radio transmitting channels thereat, a station having a radio receiver including a plurality of corresponding radio receiving channels thercat, connections for corresponding sets of transmitting and receiving channels terminating at one of said stations, trunks for each set of channels cxtending between the stations, a plurality 0t wire communication channels terminating at the. other station, means to patch the trunks at one station to the terminals of communication channels at that station, and means at the other station :for variably inter-- connecting the trunks and the communication channels terminating at the other station.

4. In a signaling system a station having a radio transmitter including a plurality ol radio transmitting channels thereat. a station having a radio receiver including a plurality of corresponding radio receiving channels thercat, connections for corresponding sets 01": transmitting and receiving channels term nating at one of said stations, trunks for each set of channels extending between the stations, :1 pluralit of wire communication channels terminat ng at the other stinion, switching means at both stations adapted to variably iuter--councct the trunks and communication channels at said stations, said switching means also serving as patching connections so that when variable connections between the trunks and communication channels are to be controlled from one station. the switching means at the other station may he used to patch the trunks to the communication channels at the other stations.

5. In a signaling system a radio transmit-- ter and radio receiver having connections leading to a common point a plurality of llll mitter and radio receiver having connections leading to a common point a plurality 01'": wire communication channels connected to said point, linlr circuits for interconnecting any wire communication channel with the radio transmitter and receiver, and means associated with said link circuits for permitting the operator to monitor the connec tion without interrupting it.

7. In a signaling system a radio trans i'nitter and radio receiver having connections leading to a common point, a plurality of wire communication channels connected to said point, link circuits for interconnecting any wire communicating channel with the radio transmitter and receiver, and switching means associated with said link circuits to enable the operators set including the transmitter and receiver to be connected with the wire circuit or the radio circuits independently.

8. In a signaling system a radio transmitter and radio receiver having connections leading to a common point a plurality of wire communication channels connected to said point, link circuits for interconnect ing any wire communicating channel with the radio transmitter and receiver, and switching means associated with said linlr circuits for enabling the operators set in cluding transmitter and receiver to be con-- nected independently either to the wire or radio part out the system, and to permit the receiver to be associated with the connection between the radio and wire part of the system without interrupting it,

9. In a signaling system a radio trans-- mitter and a radio receiver, a transmission channel extending from a common point to the radio transmitter and a receiving channel extending from a common point to the radio receiver, amplifying means associated with each channel, a plurality of wire communication channels leading to said common point, link circuits for interconnecting any wire channel with said radio transmitting and receiving channels, and means whereby the operator having control oi: said link circuits may adjust the gain in either direction at any time.

10. In a signaling system a radio transmitter and a radio receiver, a transmission channel extending from a common point to the radio transmitter and a receiving channel extending from said common. point to the radio receiver, amplifying means associated with each channel, a plurality of wire comnninication channels loading to said common point, link circuits for inter-connecting any wire channel with said radio transmitting and receiving channel and. means whereby the operator having control or said link circuits may adjust the gain in either direction at any time and means whereby the operator may observe the etiicct of the gain adjustment.

1.1. in a signaling system, a station having a radio transmitter including a radio transmitting channel, a station having a radio receiver including a radio receiving channel, connections for said transmitting and receiving channel, terminating at one of said stations, a trunk for said set of channels extending between the stations, a plurality of wire communication channels terminating at the other station, a means to patch the trunk at one station to the terminals of said communication channels at that station, and means at the other station for variably inter-connecting the trunk and the communication channels terminating at said other station.

12. lln a signaling system, a station having a radio transmitter including a radio transmitting channel, a station having a radio receiver including a radio receiving channel, connections for said set of channels terminating at one of said stations, a trunk tor said set of channels extending between the stations, a plurality of wire connnunication channels terminating at the other station, switching means at both stations adapted to variably inter-connect the trunk and wire communication channels at said. stations, said switching means also serving as a patching station so that when variable connections between the trunk and wire communication channels are to be controlled trom one station, the switching means at the other station may be used to patch the trunk to the wire communication channels at the other station.

lln testimony whereof, l have signed my name to this specification this 16th day of April, 1921.

RALPH BOWN. in testimony whereof, l have signed my name to this specification this 22nd day oi April, 1921.

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